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[ The PC Guide | Systems and Components Reference Guide | Hard Disk Drives | Hard Disk Interfaces and Configuration | Integrated Drive Electronics / AT Attachment (IDE/ATA) Interface | Unofficial IDE/ATA Standards and Marketing Programs ]
Ultra ATA (Ultra ATA/33)
With the introduction of the new Ultra DMA modes in what became the ATA/ATAPI-4 standard, manufacturers quickly adopted the new technology. The doubling of the maximum interface transfer rate was big news, and companies wasted no time trumpeting the new capabilities of the drives. One of the most common terms used to refer to these new drives was Ultra ATA, which appears to be a combination of the terms "Ultra DMA" and "ATA". Sometimes the drives were called Ultra ATA/33, referring to the maximum speed of the new Ultra DMA modes, 33 MB/s. Others called the drives just ATA/33. Still others called the drives late for dinner. ;^)
All of these are unofficial marketing terms, and not real standards. The bottom line is that even though you will see it used all the time, there really is no such thing as "Ultra ATA", at least in the official ATA standards. A drive that is marketed as using "Ultra ATA/33" is actually using Ultra DMA mode 2, which provides throughput at 33 MB/s. Some drives are sold as "Ultra DMA/33", which is a bit more accurate, but even that is a "slang" term. The correct designation for the interface of such drives would probably be "ATA-4, using Ultra DMA mode 2". That's a bit cumbersome and kind of boring, of course; I would never make a good marketing person. :^)
Note: When Ultra DMA mode
drives first started being sold, they all operated at 33 MB/s, and thus "Ultra
DMA" or "Ultra ATA" (without a number) implied mode 2 (33 MB/s). Today,
there are faster Ultra DMA modes, so be careful about interpreting what those terms mean
if no number is provided. They may be older drives using the Ultra DMA/33 standard, or the
term may be being used generically to refer to drives using any of the Ultra DMA modes.
Next: Ultra ATA/66